In semiconductor devices, a polycrystalline silicon film is used for a gate electrode or the like in some cases. With the recent scaling of semiconductor devices, it is gradually becoming difficult to form a gate electrode, which has a processed shape in which a sidewall is vertical to a substrate, by anisotropic etching.
Moreover, for example, when forming a floating gate electrode of a NAND flash memory using a silicon film, a doping amount of an impurity is modulated along a film thickness direction of the silicon film in some cases. In such a case, because the etching rate of the silicon film is different depending on a doping amount of an impurity, a constriction is sometimes formed in the center portion in the film thickness direction when processing the silicon film. Such a constriction becomes a factor of generating a void in an embedding process of a dielectric film after processing the silicon film.